The present invention relates to a polymer with increased adhesion to substrate and a resist composition containing the same. More particularly, the present invention relates to a novel polymer that is useful for preparation of a photoresist suitable for fine works using various radiations, such as KrF or ArF excimer laser, X-rays such as synchrotron radiation, and charged particle rays such as electron beam, and a resist composition containing the polymer.
With an increase in the integration density of semiconductor devices, there is a demand for super-fine patterns of which the size is 0.13 xcexcm or smaller in the manufacture of very large scale integration(VLSI). Accordingly, the radiations used as a conventional exposure source, such as g- or i-ray, have become replaced by those that have a shorter wavelength, and lithographic techniques using KrF or ArF excimer laser, X-ray or electron beam have lately attracted considerable attention. Especially, an ArF excimer laser is a most promising exposure source in the future lithography requiring a pattern size of 0.13 xcexcm or smaller.
A resist composition suitable for fine works using such radiations is composed of a component having an acid-liable functional group (hereinafter, referred to as xe2x80x9cpolymerxe2x80x9d), a component generating an acid upon light radiation (hereinafter, referred to as xe2x80x9cphotoacid generatorxe2x80x9d), and a solvent. Such a resist composition may additionally comprise a dissolution inhibitor or a base additive.
On the other hand, the polymer useful as a principal component of the resist composition is required to have a low absorbance in the wavelength range of the exposure source.
The chemically amplified resist used in the conventional radiation of a KrF excimer laser is mostly composed of a phenol-based polymer as a principal component, with a disadvantage in that the polymer shows a high absorbance in the range of the ArF excimer laser region due to aromatic rings included therein. Such a high absorbance in the wavelength range may deteriorate the perpendicularity and hence the resolution of the resulting photoresist pattern.
To solve this problem, many studies have been made on resins destitute of unsaturated hydrocarbon or aromatic group as a polymer suitable for use in a photoresist composition sensitive to an ArF excimer laser. Examples of such polymers that exhibit a relatively low absorbance in the wavelength range of the ArF excimer laser may include acrylate polymer, olefin polymer and maleic anhydride-cycloolefin polymer.
Such polymers as disclosed in the prior documents include an acrylate polymer containing an alicyclic group (See SPIE, 1996, vol. 2724, at p. 334) and a maleic anhydride-cycloolefin polymer (See SPIE, 1996, vol. 2724, at p. 355). The acrylate polymer had a low optical absorbance in the wavelength range of the ArF excimer laser but shows a poor etching resistance. The maleic anhydride-cycloolefin polymer is superior in etching resistance to the acrylate polymer but has a high optical absorbance in the wavelength range of the ArF excimer laser, resulting in poor perpendicularity of the photoresist pattern. Furthermore, the maleic anhydride monomer is liable to hydrolysis and a resist formulation comprising the maleic anhydride monomer has low storage stability.